Slow wifi on MacBook Pro when connected to Thunderbolt Display

I have run through a number of my router channels and so far not noticed a difference to the graph. It would be interesting to see if anyone else can replicate the bug and graph it too. The software I used can be downloaded here: http://www.netspotapp.com/ (there is a free version).

To replicate keep the graphing (details button on bottom left of app) open and plug in then disconnect your external monitor (using thunderbolt).

I have switched to HDMI for now and also found that moving the router slightly has helped me reach around 30-40% signal strength which is OK for my relatively slow Internet connection.

I bought a new macbook pro and a new thunderbolt display in January of 2014. My wifi speed plummets when I close the macbook pro to use the thunderbolt display. When I am in the same room as the router, the speed still drops dramatically but there is enough speed for basic internet functions. When I am farther from the router in another room, my speed drops from 22 mbps to 0.56 mbps and it is not functional. I see from other posts that others have had this problem since 2012. As near as I can tell the only solution is to arrange for overwhelming wifi speed but I haven't seen a fix for the basic problem that the wifi speed always drops dramatically when the macbook pro is closed. I went on speedtest.net and wherever I am located in the house the mbps drop dramatically when I close the notebook and try to use the display. Does anyone have an answer? My thunderbolt display is just a $1000 paperweight on my desk since I have to keep the macbook pro open to have enough wifi speed to function.

I have been having a similar problem. As I understand it, it is a combination of the wi-fi aerial operating less effecitvely when the lid is closed and the external monitor interfering with the wi-fi signal. I have found that if I close the lid (to trigger sleep mode) and then open it about an inch - not enough to wake it up - my connection is significantly improved. I have no idea why this works or whether it will do so for anyone else but it seems to help me. Good luck.

I would say this all points towards a power issue. When there is too much draw on the system (via thunderbolt) then the wifi is suffering.

Having the lid closed (or open slightly) will mean that the primary screen is off, saving power and pontentially leaving more for the wifi to do its job?

Having an external thunderbolt screen and the primary screen on is proving to be too much for the Macbooks. I doubt there is much that can be done about it via firmware either.

Closing the lid to the macbook, and then opening it an inch, helped my wifi speed dramatically when using the thunderbolt display.

I have a slightly different setup: a Macbook Pro and a Macbook Air. The MBP's screen was damaged, so I hooked it up to a typical 23" Cinema HD display (CD).

The MBA gets 37Mbps dowload when it's not connected to the CD. When it's connected, the ping time lengthens by a factor of 3-5X and the download speed drops to below 5Mbps.

I tested for interference by using the MBP to power up and illuminate the CD and then turned off the CD. The MBA gets its regular 37 Mbps regardless of whether the CD is illuminated or not.

I thus deduce that at least in my case, it's the physical connection between the MBP or MBA and the Cinema HD Display (circa 2005) that causes a sharp reduction in speed. It may not be Thunderbolt per se that's causing a problem. Perhaps physically connecting any external visuai device to a Mac causes a speed slowdown. Why this is so is beyond me, as is a solution except to test other brands to see in each case whether the problem is brand specific or general to Macs.

I am curious why this speed reduction didn't occur in a prior location, except perhaps because the top speed was so much lower the proportionate speed reduction was unnoticeable.

(By way of comparison, my Galaxy S3 smartphone gets 35+ Mbps in this environment, also, whether or not the CD is turned on and illuminated.)

Jebabc, the reason behind this is becasue the Wifi (AirPort) adapter inside your MB is designed to work best when the monitor is open (Its inside the hinge part of your screen), so when you close down your macbook and put it in camshell mode, the wifi adapter cannot recieve a good signal, as it can when its up, thus you experience slow speeds.

As for main issue, regarding Power, its nothing to do with that. I've had my MBP pluged in to my external monitor for a while now, having it as the main monitor, with the screen on the MBP up, and brightness turned off, all that time it has been pluged into the mains charging, so there is no reason for lack of power. I was doing some downloading this morning, getting as little as 25kb/s, i unpluged it from the monitor, and boom the download speed goes back up to its standard 600/700kbs.

@2014Harry - Thank you for the tip. It worked a charm. I found that with the TB external dispaly connected, having the MB lid fully open results in no reduction in my broadband speeds (25Mbps). Having the MB lid open only slightly results in a slower internet speed (16Mbps). Lastly, having MB lid shut in clamshell mode results in a very slow internet spped (1Mbps).

I first connect the TB display and close the lid. At this point the external display goes blank. I then right click the wireless mouse to wake up the external monitor and initiate the correct aspect ratio. At this point I open the MB lid fully and the MB screen remains blank, but the external display continues to operate. Perfect.

@RojSmith - Thank you for your explanation of the anatomy of the MB Pro. It makes sense that if the WiFi adaptor is located in the hinge of the MB, closing the lid will impede the WiFi signal.

Responding to my own discussion above, I have to withdraw my claim that any display attached will attenuate the wireless signal. I don't what I did or what happened, but my MPB (mid-2009) is now gettng 85% rates with the Cinema Display attached. Theory busted.

And I am another with this same issue.

Brand new, 2014 MacBook Pro Retina 13 inch with a 2011 iMac 27 inch and two different wifi routers (AT&T Uverse and the older, flat Time Capsule N. 15-22 Mbps without the screen and less than 3 Mbps (sometimes .5 Mbps) with the thunderbolt connected to the iMac.

This is killing me. Unbelievable issue Apple.

I had this issue, which I've since resolved.

I found that when I used any bluetooth peripheral, like a mouse or keyboard, while the MacBook Pro was connected to Thunderbolt the wifi was close to non existent in both open and clamshell mode. I then turned off bluetooth and wifi was reasonable. I then changed the channel the wifi signal was coming from on my router and this has cleared all wifi issues. Everything has been running smoothly since.

turning off bluetooth seems to have resolved this for me.